We plan to examine three predisposing elements in the behavioral effects of CNS drugs. The first is the strength of environmental stimulus control of behavior. Stimuli--primarily visual--will be precisely specified and then manipulated to determine how changes in behavior produced by drugs are modified by changes in stimulus parameters. Ancillary experiments will determine the degree to which drug-induced impairment of sensory function can account for these results. The second predisposing factor encompasses the degree of regulation and restriction exerted by environmental variables other than sensory stimuli; e.g., nature and extent of prior conditioning history and current schedule. Together, the above two predisposing factors represent what we consider to be the major behavioral variables that influence sensitivity to drugs. The third predisposing factor is prior exposure to low levels of drugs and environmental chemicals. The primary efforts will be directed towards chronic haloperidol with an emphasis on movement disorders. We will attempt to place the above behavioral results in a meaningful biological perspective by conducting auxiliary studies of neurochemistry and morphology, whenever possible. Since the above aims require advanced techniques for both control and analysis, we will continue to emphasize the development of new procedures that will permit a more precise detailed characterization of behavior.